Vacuumized electric switch



Feb. 13, 1962,

J. E JENNINGS VACUUMIZED ELECTRIC SWITCH Filed Sept. 16, 1958 INVENTOR. JO EMME TT JENNINGS 1611044 his AT TORNE Y description of the invention.

omitted to reduce its height.

. closed position. i a In broadly descriptive terms, the switch of my invention comprises a vacuumized ceramic cylindrical shell, ,ClOSCd at each end by a metal cover plate with which an r 3,021,407 VACUUMIZED ELECTRIC SWITCH Jo Emmett Jennings, San Jose, Calif., assignor, by mesne assignments, to Jennings .Radio Manufacturing Cor poration, San Jose, Calif., a corporation of Delaware Filed Sept. 16, 1958, Ser. No. 761,315 8 Claims. (Cl. 200-144) One of the principal objects of the invention is the provision of a vacuumized switch having an envelope large enough to holdthe heavy conductive structure and contacts required for carrying currents up to 10,000 amperes or more. I

With the development and use of electric power, there has been demand for ever larger vacuum switches to handle the increasing current loads. Expanding the diameter and capacity of vacuum switches has been severely hampered by the inherent weakness of the metalto-glass or conventional Housekeeper seal. Any increase in size of a vacuumized shell orenvelope results in a directly proportional increase in total pressure exerted by the atmosphere on all exposed surfaces of the envelope; and on an eight inch generally cylindrical evacuated envelope, the pressure tending to crush in each end amounts to more than 700 lbs. This is greatly in excess of pressures which can be borne by switches having conventional metal-to-glass unions or'seals.

' In addition to stresses imposed by atmospheric pressure, the seal structure must carry stressesimposed by the weight, sometimes considerable, of operative parts mounted on the ends, and also the shock of closing contacts and the outward jerk of opening contacts.

\ The primary object of my invention therefore is to provide means whereby a large vacuumized nonconductive cylindrical shell can be closed hermetically at its ends, and having strength in the sealing means amply sufficient to carry the heavy loads imposed by the atmosphere and its size. In a main embodiment of my invention as shown in the drawing, the ceramic shell is sealed directly to. the metal end closure structure by a heavy gauge copper plate, so that at no point in the entire envelope are weakening strains imposed by atmospheric pressure or by the stresses of expansion and contraction.

The heavy gauge copper plates at top and bottom are .of different shape, and have certain different functions and purposes despite their common purpose of providin vital eleinentsin an all-metal seal. a y

Another object is the provision of a vacuumiz'ed switch of very large capacity housed in a cylindrical dielectric shell, closed hermetically at each end by a simple plate tructure hermetically united to the shell by all-metal sealing means including a readily accessible joint at which the seal may be broken to give access to the interior of the switch, the seal then being capable of being reformed, and the switch envelope again vacuumized for further use.

Other objects will be brought out in the following I do not limit myself to the showing made by said description and the drawings, since I may use variant forms of the invention within the scope of the appended claims.

With reference to the drawing which is approximately full size, the figure is a half-sectional view of a switch embodying my invention. A portion of the figure is I The switch is shown in ice Patented Feb. 13, 1962 integral union, and therefore hermetic seal, is effected- This integral union is formed by a copper skirt of substantial thickness throughout, brazed at its inner edge to the metallized edge of the ceramic shell, and at its outer edge integrally united to the plate, by a steel flange at the upper end of the shell, and directly at the lower end.

At the upper end, the freeledges of flange and skirt are contiguous, and extend around the cylindrical shell on the outside at a short distance therefrom, so that the two edges are readily joined by a heliarc weld, and as easily cut apart when needarises. The free portion of the skirt preferably conforms substantially to a conical plate, flaring outwardly and downwardly. At all points the sealing skirt is a" thickness amply sufiicient to withstand any probable stress placed upon it in normal use of the switch without damaging strain. The lower end of the ceramic shell is provided with a skirt which also seals it integrally to the lower end plate, but in thiscase the skirt is not intended to be severed to free the end but only to provide an all-metal seal, and avoid a trap for external moisture and dirt.

Within the envelope formed by the cylindrical shell and end plates, switch elements are arranged. A fixed contact is mounted within the shell on one end plate; and an axially aligned mobile contact is slidably journaled on the other end plate, a bellows being interposed between bearing and mobile contact to preserve the vacuum within the shell.

The mobile contact of the switch is fixed on the inner end of an operating stem within the vacuumized envelope and in axial alignment with the fixed contact. The stem extends'out of the open end of the bellows in a portion adapted'for connection to a conductor; and is tact to open the circuit. The bellows permits both movements without break in the vacuum of the enclosing envelope. i I

In detail my switch comprises a cylindrical ceramic shell 2., around the upper metallized edge 3 of which is brazed a skirt 4 of copper having substantially an even thickness throughout. The copper skirt flares outwardly from the shell, in a substantially conical conformation, terminating ina free edge 5, lying snugly against the inner surface of the cylindrical steel flange 6, brazed into a groove in the lower face of the upper plate 7. The

contiguous edges of flange and skirt are readily accessible and may be readily brazed together to form the joint 8 by the heliarc process. They are also readily separated if necessary to give access to the switch parts.

Mounting holes 9 are formed about the rim ofeach end plate; and a metal tubulation It) is brazed to the plate 7 in continuation of the passage 12 by which the switch envelope is connected to the processing pump. A heavy copper cylindrical mounting block 13 is brazed into a recess concentricallyformed on the inside face of the upper end plate; and on its inner face is fixed the tungsten contact or electrode '14. These heavy parts thus provide ample conduction for heavy currents and escape for generated heat. A cap screw 15 provides means for connecting the fixed end of the switch to a conductor 16. I

It will be observed that this structure, provides a hermetically tight upper end for the shell; and that the stressesimposed by atmospheric pressureare carried by the all-metal seal 4 -6 and by the end plate 7, which in addition supports the mounting block and fixed contact. It also carries the shock and thrust of the closing contacts.

In the lower portion of the shell is the mobile tungsten contact or electrode 17 mounted in the head 13 of thesolidcopper stem 19. The stem is slidably journaled in a fixed bearing tube 21 having a wide flange 1 2 and concentrically arranged on and secured by screws 23 to the lower end plate .24 of which it forms the central hearing portion.

Expansible means, preferably a metal bellows 26 is interposed between the lower end plate and the stem 19 to permit axial movement of the stem to open and close the switch without destroying the vacuum within the envelope.

All-metal sealing means is provided at the lower end of the shell 2 for hermetic securement to the lower end plate, so that stresses caused by expansion and con traction are accommodated in a manner somewhat similar to that found in the upper all-metal seal. The plate is provided wtih a circular and concentric groove 27. An annular copper plate 28 having a short outer peripheral flange 29 and a central downwardly extending bead 31, is brazed to the metallized lower edge of the shell, the bead lying loosely in the groove 27 and the flange 2.9 brazed into a corresponding shallow groove in the plate. An annular ring 32 may overlie the upwardly opening bead if desired to prevent accumulation therein of foreign matter.

Brazed to the inner periphery of the apertured lower plate is a shield .33 surrounding the bellows and protecting itfrom, bombardment and injury by the flying hot tungsten particles at times thrown off the contact points of the switch. The lower edge 34 of the shield projects past the narrowed inner edge 36 of the plate so that a free margin is left under the overlying bearingflange 22 for convenient integral union as by heliarc to the adjoining lower flange 37 of the bellows. This integral union 38 unites the bellows to the lower plate.

The upper end 39 of the bellows is brazed to the upper end of the stem under the head 18 along with the battles or shields ll and 42, the latter having the outwardly and upwardly flaring flange 43. The shield 41 is provided with a downwardly directed flange 44- ending closely adjacent to the rim 4-6 of the surrounding shield 33.

The shape, size and placement of the three shielding surfaces 33, 44 and 43 are such that in operation of the switch, the flying high speed hot particles of tungsten torn oil the switch points are prevented from striking the bellows. Only relatively few slow moving infinitely small particles will drift at low velocity through the very narrow annular space between the shields 33 and 44.

The stem 19 extends downwardly out of its bearing, in a portion 47, adaptedto receive a clamp connector 48 for the direct and positive connection of the conductor 49 to the stern and tungsten contact, thus avoiding any sliding connection through the switch capable of spark-welding relatively moving parts together. The end of the stem includes a brass bushing 51 brazed externally to the stem, and threaded internally to receive a threaded stud 52 which rigidly connects the stem to the dielectric link 53 of Teflon or equivalent non-conducting material. A rod 54 threaded into the outer end of the link 53 completes the connecting link between the stem 19 and the operator which may be a solenoid or other appropriate means.

The respective diameters of the three shields is also important because in the event that it is necessary for inspection or repair to gain access to the interior of the envelope, the clamp 48 and conductor 49, and the link element $3 are disconnected; and the screws 23 removed. The bearing tube 21 with its flange 22 can then be drawn oil of the stem.

By severing the union 3%, the vacuum is destroyed and the assembly of bellows, stem and shields 43 and 44 may then be withdrawn from the envelope through joint or joints opened, the tubulation can be again connected to the pump and the unit processed as before.

I claim:

1. In a vacuumized electrical implement, a dielectric cylindrical shell, an end plate having a central opening, means integrally uniting the end plate to one end of the shell, a bearing extending through said central opening of the plate into the shell and having a flange fixed to the end plate and extending across the central opening, a stem journaled in the bearing, and a bellows at one of its ends integrally connected to the stern and at its other end integrally connected to and functionally severable from the end plate, said central opening of the end plate being larger than the largest diameter of the bellows to permit passage of the bellows and attached stern therethrough in assembly and disassembly.

2. In a vacuumizedelectrieal implement, a dielectric cylindrical shell, an end plate having a central opening, means integrally uniting the end plate to one end of the shell, a bearing having a flange fixed to the end plate and extending across the central opening, a stern journaled in the bearing, an annular flange integral with the end plate and extending into the opening, and a bellows extending intothe shell and at one of its ends integrally connected to the stem and at its other end terminating in an annular flange contiguous to the end plate annular flange and integrally united therewith, said central opening of the end plate being larger than the largest diameter of the bellows to permit passage of the bellows and attached stem therethrough in assembly and disassembly.

3. In a vacuumized electrical implement, a dielectric cylindrical shell, an end plate having a central opening with an annular relatively thinner flange extending from the edge thereof into the opening, means integrally uniting the end plate to one end of the shell, a bearing having a flange fixed to the end plate and extending across the central opening, a stem journaled in the bearing and extending as a connector stud outside of the flange, a bellows extending into said shell and enclosing said bearing and at one of its ends integrally connected to the stem and at its other end integrally connected to the thinner flange of the end plate, and dielectric means fixed to the connector stud for securing the stud to an operator for the stem, said central opening of the end plate being larger than the largest diameter of the bellows to permit passage of the bellows and attached stem therethrough in assembly and disassembly.

4. In a vacuumized electrical implement, a dielectric cylindrical shell, an end plate having a central opening, means integrally uniting the end plate to one end of the shell, a bearing having a flange fixed to the end plate and extending across the central opening, a stem journaled in the bearing and extending therebeyond into the shell, a bellows at one of its ends integrally connected to the stem beyond the bearing and within the shell and at its other end integrally connected to and functionally severable from the end plate outside the shell, and an electrode fixed on the inner end of the stem.

5. In a vacuumized electrical implement, a dielectric cylindrical shell, an end plate having a central opening bordered by an exposed flange, means integrally uniting the end plate to one end of the shell, a bearing having a flange detachably fixed to the end plate and extending across the central opening over the exposed flange, a stern journaled in the bearing, a bellows at one of its ends integrally connected to the stem and at its other "severed.

central opening through the end plate when the integral connection between bellows end and exposed flange is 6. In a vacuumized electrical implement, a dielectric cylindrical shell having its end edges metallized, an end plate overlying the upper end of said shell, an end plate having a centralopening therein and overlying the lower end of said shell, an expansible annular skirt outside each end of the shell and integrally connected at its inner periphery to the shell end edge and at its outer periphery to the end plate, an annular relatively thinner flange integral with the lower end plate and extending into the opening, a bearing having a flange fixed to the lower end plate and extending'across the central'opening, a stem journaled in the bearing, a bellows at one of its ends integrally connected to the stem and at its other end integrally connected to the thinner flange of the end plate, and aligned electrodes within the shell and mounted respectively on the upper end plate and on the stem said end plates being spaced closely to the respective end edges of the shell by approximately the'thickness of said skirt at its inner periphery.

7. An all-metal seal for a vacuumized envelope having a dielectric cylindrical shell closed by a metal plate having an upwardly opening groove therein concentric with the shell, comprising a metallized edge on the shell, and an annular beaded metal skirt adjacent the end of 1,011,160 Cofiin Dec. 12, 1911 1,905,751 Rankin Apr. 25, 1933 2,314,266 Beam Mar. 16, 1943 2,326,074 Slepian Aug. 3, 1943 1 2,773,154 Williams Dec. 4,1956 2,794,101 Jennings -e. May 28, 1957 2,854,550 Gerth et al, Sept. 30, 1958 2,863,027 Jennings Dec. 2, 1958 2,892,912 Greenwood et al June 30, 1959 2,900,476 Reece Aug. 18, 1959 i 2,916,577 Smith Dec. 8, 1959 2,920,169 Jennings Jan. 5, 1960 FOREIGN PATENTS Germany Nov. 3, 1932 the shell and having one periphery integrally connected 2 to the edgeof the shell and the other periphery integrally connected to the closing plate with the head in the groove.

8. An hermetic seal betweenthe metallized terminal end surface ofa hollow ceramic shell and a metal end plate, comprising a radially, shaped annular ring surrounding the shell and integrally connected along one of its edges with the end plate, and the other edge being integrally united to the metallized terminal end surface by approximately the thickness of said annular ring.

References Cited in the file of this patent UNITED STATES PATENTS 

